Crash after Enabling Forward Shading on Mac and Creating/Editing Materials

A crash occurs after enabling 'Forward Shading' on Macs. The crash is triggered after creating a new material and attempting to modify that material.

Regression?
No, this crash also occurs in the 4.13.2 release.

I have attached the crash logs from both 4.13.2 and the 4.14 releases for investigation.

1. Create new project.
2. Go to Project Settings > Rendering > Forward Shading and check it to true.
3. Restart project when prompted.
4. Wait for Shaders to compile.
5. Create new Material and attempt to edit the material. (Add Vector3) etc.

Outcome A crash occurs shortly after creating and opening the material to edit its properties.

Expected No crash occurs

UE4Editor-MetalRHI.dylib!FMetalRHICommandContext::RHISetShaderUniformBuffer()
UE4Editor-Renderer.dylib!void FForwardLightingParameters::Set<FRHICommandList, FRHIPixelShader*>()
UE4Editor-Renderer.dylib!TBasePassPixelShaderPolicyParamType<FUniformLightMapPolicyShaderParametersType>::SetParameters()
UE4Editor-Renderer.dylib!TBasePassDrawingPolicy<FUniformLightMapPolicy>::SetSharedState()
UE4Editor-Renderer.dylib!void FDrawBasePassDynamicMeshAction::Process<FUniformLightMapPolicy>()
UE4Editor-Renderer.dylib!void ProcessBasePassMesh<FDrawBasePassDynamicMeshAction>()
UE4Editor-Renderer.dylib!FBasePassOpaqueDrawingPolicyFactory::DrawDynamicMesh()
UE4Editor-Renderer.dylib!FRendererModule::DrawTileMesh()
UE4Editor-Engine.dylib!FTileRenderer::DrawTile()
UE4Editor-Engine.dylib!FCanvasTileRendererItem::Render_RenderThread()
UE4Editor-Engine.dylib!FCanvas::Flush_RenderThread()
UE4Editor-GraphEditor.dylib!FPreviewElement::DrawRenderThread()
UE4Editor-SlateRHIRenderer.dylib!FSlateRHIRenderingPolicy::DrawElements()
UE4Editor-SlateRHIRenderer.dylib!FSlateRHIRenderer::DrawWindow_RenderThread()
UE4Editor-SlateRHIRenderer.dylib!TGraphTask<FSlateRHIRenderer::DrawWindows_Private(FSlateDrawBuffer&)::EURCMacro_SlateDrawWindowsCommand>::ExecuteTask()
UE4Editor-Core.dylib!FNamedTaskThread::ProcessTasksNamedThread()
UE4Editor-Core.dylib!FNamedTaskThread::ProcessTasksUntilQuit()
UE4Editor-Core.dylib!FTaskGraphImplementation::ProcessThreadUntilRequestReturn()
UE4Editor-RenderCore.dylib!RenderingThreadMain()
UE4Editor-RenderCore.dylib!FRenderingThread::Run()
UE4Editor-Core.dylib!FRunnableThreadPThread::Run()
UE4Editor-Core.dylib!FRunnableThreadPThread::_ThreadProc()
libsystem_pthread.dylib!<Unknown>
libsystem_pthread.dylib!<Unknown>
libsystem_pthread.dylib!<Unknown>